Abstract 50

Introduction Interleukin-1β (IL-1β) is a major pro-inflammatory cytokine released during neonatal sepsis. Its bioactivity, however, is difficult to determine since it has several antagonists. Longitudinal changes in the concentrations of IL-1β, IL-1 receptor antagonist (IL-1ra) and the soluble form of the type II receptor of IL-1 (IL-1sRII) were measured in babies admitted to the NNU and the relationships between them analysed to determine the bioactivity.

Method Serum concentrations of the 3 ligands were measured at predetermined times over 3 weeks in 26 neonates (mean gestation=29wks), yielding 135 samples.

Results Median concentrations and median ranges (pg/ml) were IL-1β=0.8 (undetectable-3.44), IL-1ra=5600 (1313-30000), and IL-1sRII = 17000 (13190-23250). For each patient the median variation between peak and trough concentrations were IL-1β=340 fold, IL-1ra=22 fold, and IL-1sRII = 1.8 fold. Graphically, fluctuations in the concentrations of each cytokine correlated.

Conclusion Concentrations of IL-1sRII were 4 fold higher than IL-1β and only minor fluctuations were seen. This does not add any extra information about IL-1β bioactivity, but supports the theory that IL-1sRII may be a sump for IL-1β. IL-1ra fluctuations were less than IL-1β, but sufficient to add information about bioactivity.